RE: [PATCH] PowerPC, fix gdb.base/retval-large-struct.exp

[Carl Love <cel@us.ibm.com>]

Tom:

On Fri, 2022-11-18 at 17:25 +0100, Tom de Vries wrote:
> On 11/18/22 17:04, Ulrich Weigand wrote:
> > Tom de Vries <tdevries@suse.de> wrote:
> > 
> > > AFAIU, needing -fvar-tracking is specific to powerpc, so we
> > > should limit
> > > it's impact to that target.
> > > 
> > > And it's a gcc compiler flag, so perhaps we should limit it's
> > > impact to
> > > that as well.
> > 
> > No, it's not really powerpc specific - the same mechanism can be
> > used on many other platforms with an ABI that uses a return buffer
> > address that is not preserved.  (E.g. we're currently looking into
> > enabling it on s390x.)
> > 
> 
> Right, so we can add those archs to the list of archs requiring 
> -fvar-tracking support when gcc is used.
> 
> > And given that the flag is harmless if it's available (which the
> > test verifies), I think it makes sense to just always enable it.
> > 
> 
> That's fine by me.
> 
> Then I get:
> ...
> set flags {}
> 
> lappend flags debug
> 
> if { [have_fvar_tracking] } {
>      lappend flags -fvar-tracking
> } else {
>      if { ( [istarget powerpc*-*-*] || [istarget s390x*-*-* ])
>           && [is_c_compiler_gcc] } {
>          unsupported "gcc used, -fvar-tracking needed"
>          return -1
>      }
> }
> 
> if {[prepare_for_testing "failed to prepare" $testfile $srcfile
> $flags]} {
>         return -1
> }

The [have_fvar_tracking] does a runtime test to see if the compiler
supports the -fvar-tracking option.  So if it passes, then the option
is supported.  The test makes the additional check  [istarget powerpc*-
*-*] || [istarget s390x*-*-* ]) && [is_c_compiler_gcc]  redundant.  

I don't think there is any need for the additional checks.

                  Carl